Heat exchanger



prll 2l, 1936.v W C;- NOACK 2,037,814

' HEAT EXGHANGER Filed July 2o, 1935 v 2 sheets-sheet 1 37 v I 5 JZIZIenZm/z W. G. NoAcK HEAT EXCHANGER Filed July 2o, 1955 2 Sheets-Sheet 2 April 21, 1936.

Patented pr. 2l, i936 HEAT' EXCHANGER Walter Gustav Noaek, Baden, switzerland, as-

sgnor to Aktiengesellschaft Brown, Boveri itJ Cien-Baden, Switzerland Application July 20, 1933,-Serial No. 681,344 In (Slermany July 26, 1932 19 Claims.

This invention relates to tubular heat exchangers consisting of a plurality of tubes arranged` tuses whereby the joints are of such configuration as to constitute a very small resistance to the ow ofthe heat carrying mediums.

An object of this invention resides in the pro-A vision of a heat exchanger wherein practically all eddy currents, dead corners, etc. which cause a loss of energy of the heat exchanging mediums and an increase of heat by the creationof frictional heat in the medium supplying the heat are definitely eliminated.

An object o f this invention resides in the provision of a heat exchanger having a plurality of tube sections which consist of a plurality of individual tubes connected by nipples which have a streamline configuration and constitute practically no resistance to the flow of the heat exchanging medium and theA ends 'of the sections abut against each other whereby each tube has a continuous, uninterrupted surface over which the heat exchanging medium outside of the tubes ilowsg at high velocity along and substantially parallel to the axis of the tubes.

Further and other objects of the present in- -vention will be hereinafter set forth in the accompanying specification and claims and shown in the drawings which, by way of illustration, show what I now consider to be a'preferred embodiment of my invention.

In the drawings: l

Fig. 1 is a longitudinal section through a-heat exchanger according to my invention.

Fig. 2 is a large scale cross lsection through a heat exchanger as shown in Fig. 1 and taken along line 2--2 of Fig. 1.

Figs. 3 and 4 are longitudinal sections through a tube-joint according to my invention, Fig. 3 being taken along line 3-3 of Fig. 4 and Fig. 4 along line 4--4 of Fig. 3.

Fig. 5 is a longitudinal section along line 5-5 of Fig. 6 through a joint Yat the end of a tubular element. l

Fig. 6 is a view partly in section along line 6-6 of Fig. 5 of a plurality of joints according to my invention.

-heat transfer conditions.

Fig. 'iis a. longitudinal section along line 'l-l of Fig. 8 through a modification of a tube joint according to my invention.

Fig. 7a illustrates a detail of the manufacturing process of a joint according to my invention. 5

Fig. 8 is Va longitudinal section along line 8-8 of Fig. '7 through a tube section according to my invention. A

Fig. 9 is a longitudinal section through a welded and reinforced tube joint.

Fig. 10 illustrates a pair of pliers for manufacturing a joint according to Fig. 9.

Fig. 11 is a longitudinal section through a cast tube joint having reinforcements according to my invention.

Fig. 12 shows a tube joint as disclosed in Fig. 11 with part of the joint broken away.

Referring more particularly to the drawings:`

Fig. 1 discloses a heat exchanger according to my invention operating as economizer or superheater of a steam generator and being heated by hot combustion gases passing at high velocity through a duct I8. The heat exchanger is built of three sections I, 2 and 3 arranged on top of each other. Each section is built of seven groups I9 each consisting of seven tubes as is apparent from Fig. 2. The water to be preheated or the steam to be superheated circulates inside the tubes. It enters the heat exchanger through' conduits 4 and leaves it through conduits 5. The in- 30 dividual groups I9 of one section are connected to the individual groups of another section by the elbow pieces 6 and 'I which are accommodated in boxes 20 and 2| attached to the duct I8. The direction of the flow of the heating gases is substantially parallel to the outside of the tubes of the heat exchanger; the gases enter the duct I8 at the bottom through an elbow 8 and leave the duct through a cone-shaped uptake 9. Since the velocity of the heating gases should be great in 40 order to transfer great amounts of heat into the tube sections per square foot of heat absorbing surface, everything which would act as a resistance to the free flow of the heating gases must be avoided unless it improves at the 'same time the 45 In order to obtain a very high heat transmission I may use gas velocities of 150 to 300 and more feet per second.I By widening out the uptake the high velocity of the gases is again reduced when leaving t'ne heat ex- 50 changer and the kinetic energy of the rapidly moving gases again converted into static or pressure energy which can be used to force the gases into other ducts connected to the uptake 9 or to blow them out into the atmosphere. If the usual transverse tube connections are employed or the tubes are bent like hairpins the free area available for the flow of the gases is very much reduced and the gases must be accelerated to several times the speed at which they ow along the tubes in the other part of the heat exchanger which requires great pressure and energy to produce this pressure. A reduction of free area and acceleration of the gases produces whirls and eddy currents which further increase the resistance to the iiow of the gases and necessitate high gas pressure for overcoming this resistance. According to my invention the tube joints are made of streamlined bodies. Figs. 3, 5, '1, 9, and l1 showl such streamlined joints. They are considerably smaller or rather narrower than the tubes which they connect. The reduction of the free area of the channel between the tubes for the heating gases is therefore almost negligible. The power required to produce the corresponding acceleration of the gases is small since, owing to the par-v certain amount of the gases per time unit through the joints is converted again into pressure energy` as soon as the gases leave the joints. The connecting piece may be cast and serve for the connection of two tubes as per Figs. 3 and 4, or cast or forged bodies as per Figs. 5 and 6 may be used to connect a whole group of tubes. Just as important for the elimination of ow losses by suitably shaping the transverse connections of the tubes is the elimination of losses caused by staggering the tubes. To secure-a minimum reduction of free area and a straight now of the gases along the tubes it is necessary that all tubes be in line and that the surface of the section of one tube be flush with the surface of the next section. That is, each tube of each section is in alignment with the corresponding tube of every other section.

The joint illustrated in Figs. 3 and 4 answers both requirements. The upper part 22 of the joint connects the tubes 29 and 3l) of one tube section for example section 3 and is provided with the connection or nipple 23 having an opening I3 for the water or steam or other matter to be heated and circulated for example from tube 29 into tube 30. The connection 23 has a streamline form, the outside contour converging from a. comparatively wide distance 28 into a point 24. The lower part 25 of the joint connects the tubes 3| and 32 of another tube section for example section 2 and is provided with a connecting channel 26 having an opening I4 for permitting the water, steam or other matter circulating within the tubes to pass freely therethrough and having a streamlined outside contour with a rounded end 21, a slight diversion of the outer surfaces and again a conversion of these surfaces to the distance 28 which is equal to the distance of the surfaces at the end of the upper part 22. Upon abutment of connecting bodies 23 and 26 a continuous streamline body is obtained. In order to answer the second requirement, namely, the abutment of the tube ends and an uninterrupted flow of the heating gases along and outside of the tubes, the connecting piece 22 is provided with a iiat bottom having plugs II and I2 which are screwed into projections I0. By removing the plugs I I and I2 the interior of the tubes 30 and 29 is accessible for example for cleaning purposes. Connection piece 25 is also provided with a bottom 34 having recesses 35 for 'accommodating the plugs I I and I2. It is obvious that upon abutment of the bottoms 33 and 34 at their fiat rim 36 the two tubes sections 2 and 3 are maintained in a fixed position to each other and a smooth flow of the gases along the tubes is assured.

Figs. 5 and 6 show an embodiment of my invention as used for connecting a plurality of tubes and for connecting the lower ends of the tubes of the lowermost tube section I and the upper tube ends of the upper-most tube section 3. The body 31 may be made of cast steel or cast iron or forged and welded to the tubes 38. 'I'he parts I6 connecting the interior of the tubes have a streamline outside contour which is more particularly apparent from Fig. 5. The parts I5 connecting the tubes at the outside serve for stiifening the whole section. 'I'hey also have a streamline outside contour but can be made much smaller and narrower than the parts I6 which must be wider to provide for the opening for the flow of the liquid or steam. 'I'he parts I5 may also be higher up on the tubes to further facilitate the free ow of the heating gases or they may be staggered.

Figs. 7 and 8 show a joint according to my invention whereby no special connecting piece is used but whereby the tube itself is squeezed outwards and the resulting projecting parts are welded together. Such a joint may be made in the following manner: at first holes 39 (Fig. 7a) are drilled into the tube and a saw cut 40 made to connect the holes; then a pair of pliers or a squeezer as per Fig. 10 having a projecting part 4I and a female part 42 of cone-shaped configuration corresponding to the shape of the opening 43 to be produced is inserted into the tube and the saw cut 40 is widened out by the projection 4I of the squeezer thereby producing the opening 43. The projecting rims 44 are then welded together. Tube connections which must withstand high internal pressures may have two openings 45 and 46 as shown in Fig. 9 whereby a pin 41 connects the outer rims 44 of the connection. This pin is welded to the rims. For producing such a joint the projecting part of the squeezer as shown in Fig. 10 is provided with a recess 48 and the female part with a corresponding projection 49. This produces an interruption of the rim 44 which may be drilled out for providing an opening for the pin 41.

When using cast steel or cast iron connecting pieces to be welded to the tube ends for high internal pressures, these are preferably provided with reinforcements 50 as indicated on Fig. 11. The joint illustrated in Figs. 11 and 12 can be advantageously used to connect those ends of the Y tubes which are located where the gases enter and leave the heat exchanger similar to the connection illustrated in Figs. 5 and 6. The connection has a pointed end 5I which facilitates the entrance of the gases between the tubes and is also provided for a gradual opening up of the free area for the gas flow at the point where the heating gases leave the heat exchanger.

A heat exchanger built according to the foregoing description is reliable in its operation. Even if it is heated by combustion gases containing great amounts of dust, a settling down of the dust on the heating surfaces is not possible as the surfaces have no corners or the like and the gases pass along the surfaces at very high velocity and continuously and effectively brush all of the heating surfaces. The heating gases may also be cooled off, for example if the exchanger is used as an economizer, to a temperature much lower than is usually advisable in such apparatuses. Since there are no dead corners or the like where condensate from the vapor contained in the combustion gases or leakage water could settle down and stay for some time the vformation of corroding acids is not possible. On the contrary, thecondensation may even be desirable in order to utilize the heat of evaporation of the steam contained in the combustion gases and transfer it to the water to be preheated-a heat which otherwise goes out through the stack. Due to the high velocity of the heating gases any drops forming on the cold tube walls are blown away and carried by the gases to the outside and a formation of harmful acids or a re-evaporation of such drops in thev flue gases is denitely prevented.

I wish it to be understood that I do not desire to be limited to the exact details of process, design and construction shown and described for obvious modifications will occur to a person skilled in the art.

What I claim is:

1. In a heat exchanger having a casing through which a heat exchange medium flows, a plurality connecting bodies for externally spacing adjacent internally separated tubes.

'7. A heat exchanger in accordance with claim 2 in which the hollow connecting bodies for inof fluid conducting tubes having their ends closed,

the line of flow of the heat exchange medium4 through the casing, and a plurality of hollow connecting bodies having stream line outer contours connecting said fluid conducting tubes to provide a' passageway through the tubes for the fluid therein and facilitate the flow of the heat exchange medium throughcthe casing. 2. In a heat exchanger having a casing through which a heat exchange medium flows, a plurality of sections for conducting fluid in said casing, each fluid conducting section comprising a plurality of fluid conducting tubes having their ends closed, positioned within said casing and extending along the line of ilow of the heat exchange medium through the casing with the ends of the tubes of one section abutting the ends of the tubes of the next succeeding section in the casing, a plurality of hollow connecting bodies providing connections between the fluid conducting tubes of each section to provide a passageway through the tubes of each section for the fluid therein, each section having an inlet at one end and an outlet at its other end, and a hollow connecting means between the outlet and inlet of each adjacent abutting section.

3. A heat exchanger in accordance with claim 2 wherein one of the ends o f the tubes of two endwise abutting tube sections is provided with clean 4out end openings and projecting plugs for closing the sameand the corresponding ends of adjacent section pipes are provided with recesses for accommodating said projecting plugs and permit the pipe ends of the corresponding section to be positioned in a closely abutting relationship.

4. A heat exchanger in accordance with claim 2 wherein the remote ends of the tubes of the two end fluid conducting sections are formed with stream line outer contours.

5. A heat exchanger in accordance with claim 2 wherein the remote ends of the tubes of the two end iiuid conducting sections are formed with stream line outer contours and hollow connecting bodies for internally connecting tubes to provide fluid passageways at said ends of said tubes are likewise formed'with streamline outer contours.

6. A heat exchanger in accordance with claim 2 wherein remote ends of the tubes of the two end iluid conducting sections are provided 'with ternally connecting tubes to provide fluid passageways at the remote ends of tubes of the two end fluid conducting sections are formed with stream-line outer contours. 8. In a heat exchanger having a casing throug which a heat exchange medium flows, a plurality of sections for conducting fluid in said` casing, eachl fluid conducting section comprising a plurality of fluid conducting tubes having their ends closed, positioned within said casing and extending along the line of flow of the heat exchange medium through the casing with the ends of the tubes of one section abutting the ends of the tubes of the next succeeding section in the casing, a plurality of hollow connecting bodies providing connections between the fluid conducting tubes of each section to provide a passageway through the tubes of each section for the fluid therein, said hollow connections at abutting ends of sections having abutting ends and each pair of such abutting hollow body connectors forming individual passageway for the iluid in the corresponding sections, each section having an inlet at one end and an outlet at its other end, and a hollow connecting means between the outlet and inlet of each adjacent abutting section.

9. A heat exchanger in accordance with claim 8 in which each pair of abutting hollow body connectors have their outer surfaces as an entirety of streamline formation.

10. A heat exchanger in accordance with claim 8 in which the closed ends of the tubes and the connector members form substantially ilat sur- -corresponding projections which are accommodated in the recesses of the rst section.

12. In a heat exchanger having a casing through which a heat exchange medium flows, a plurality of fluid conducting tubes positioned within said casing extending along the line of flow of the heat exchange medium through the casing, and connections for laterally spacing and interconnecting the extreme ends of the tubes in the casing, said connections having a streamline outer contour with a rounded point Where the heat exchange medium first contacts them and then converging in the direction of flow of said medium to a sharp point to facilitate the flow of the heat exchange-medium through the casing.

13. In a heat `exchanger in accordance with claim 12 in which some of said connections are hollow to provide interior passageways between tubes and others provide exterior connections between tubes.

14. In a he'at exchanger in accordance with claim 12 in which some of said connections are hollow to provide interior passageways between tubes and are each provided with a reinforcement subdividlng the openings through the connections.

15. In a heat exchanger in accordance with -claim 12 in which some of said connections are hollow to provide interior passageways between tubes and are each provided with reinforcing partitions subdividing the openings through the connections.

16. In a heat exchanger having a casing through which a heat exchange medium flows, a plurality Qf fluid conducting tubes positioned within said casing extending along the line of ow of said heat exchange medium through said casing, and connections for laterally spacing and interconnecting the extreme ends of said tubes in said casing, said connections having a streamline outer contour and consisting of bulged out parts of said tubes.

17. In a heat exchanger having a casing through which a heat exchange medium ows, a plurality of uid conducting tubes positioned within said casing extending along the line of ow of said heat exchange medium through said casing, and connections for laterally spacing and interconnecting the extreme ends of said tubes in said casing, said connections having a streamline outer contour and consisting of bulged out parts of said tubes, whereby the bulged out part of one tube is welded to the bulged out part of the next adjacent tube.

18. In a heat exchanger having a casing through which a heat exchange medium flows, a plurality of fluid conducting tubes positioned within said casing extending along the line of ow of said heat exchange medium through said casing, and connections for laterally spacing and interconnecting the extreme ends of said tubes in said casing, said connections having a streamline outer contour, being hollow" to provide interior passageways between tubes, consisting of bulged out parts of said tubes, and being provided with a reinforcement subdividing the openings through said connections.

19. In a heat exchanger having a casing through which a heat exchange medium flows, a plurality of fluid conducting tubes positioned Within said casing extending along the line of iiow of said heat exchange medium through said casing, and connections for laterally spacing and interconnecting the extreme ends of said tubes in said casing, said connections being hollow to provide interior passageways between tubes and having an outer contour which is streamlined in the direction of flow of said heat exchange medium.

WALTER GUSTAV NOACK. 

